Natural Radiation Survey and Analysis Research Unit, Department of Nuclear Engineering, Faculty of Engineering, Chulalongkorn University, 10330, Bangkok, Thailand; Institute of Radiation Emergency Medicine, Hirosaki University, 0368564, Aomori, Japan.
Natural Radiation Survey and Analysis Research Unit, Department of Nuclear Engineering, Faculty of Engineering, Chulalongkorn University, 10330, Bangkok, Thailand.
J Environ Radioact. 2021 Apr;229-230:106506. doi: 10.1016/j.jenvrad.2020.106506. Epub 2021 Jan 17.
In this study, a portable cascade impactor was developed to more efficiently determine the activity size distribution of attached radon and thoron progeny in a natural environment. The developed impactor consisted of four stages with a backup filter stage for collection of the aerosol samples. The aerosol cut points were set for 10, 2.5, 1, and 0.5 μm at a sampling rate of 4 L min. Five CR-39 chips were used as alpha detectors for each stage. To separate the alpha particles emitted from radon and thoron progeny, the CR-39 detectors were covered with aluminium-vaporized Mylar films. The thickness of each film was adjusted to allow alpha particles emitted from radon and thoron progeny to reach the surface of the CR-39 detectors. The particle cut-off characteristics of each stage were determined by mono-dispersive aerosols with particle sizes ranging from 0.1 to 1.23 μm from the collection efficiency curve. The test results showed that the respective cut-off size of stages 3 and 4 were close to the designed cut-points. Validation of the technique by comparison with two commercial devices confirmed that the developed technique could provide the necessary information to estimate the activity size distribution of attached radon and thoron progeny for dose assessment, especially, in a field survey where direct electric power is not available.
在这项研究中，开发了一种便携式级联冲击器，以更有效地确定自然环境中附着氡和钍子体的活性大小分布。所开发的冲击器由四个阶段组成，在收集气溶胶样品时还有一个备用过滤器阶段。气溶胶切割点设定为在采样率为 4 L min 时为 10、2.5、1 和 0.5 μm。每个阶段使用五个 CR-39 芯片作为α探测器。为了分离氡和钍子体发出的α粒子，将 CR-39 探测器用铝蒸发聚酯薄膜覆盖。每个薄膜的厚度都进行了调整，以允许从氡和钍子体发出的α粒子到达 CR-39 探测器的表面。通过收集效率曲线，使用粒径范围为 0.1 至 1.23 μm 的单分散气溶胶确定了每个阶段的颗粒截止特性。测试结果表明，第 3 阶段和第 4 阶段的各自截止尺寸接近设计的截止点。通过与两种商业设备的比较验证该技术，证实了所开发的技术能够提供必要的信息，用于评估剂量，特别是在没有直接电力的现场调查中，估计附着氡和钍子体的活性大小分布。
